The removal of watchlists has sure taken some degree of convenience from wardeccing. Back when notifications weren't a thing, you still could add a character to the watchlist and see him log in while doing something else. Notifications made it mucho easier: you could easily leave your intel guy AFK for the day and learn everything about your targets' logging petterns upon return.
There is still a workaround to the lack of the watchlist: you can send your target a convo request. If he's online, he'll respond, reject or leave it without reaction (if AFK). In case he's offline, you'll get an offline message accordingly, even if the character in question has your pinging character blocked. Thankfully, convo requests don't expire, unlike fleet invites.
This means that wardeccing now involves a good deal of manual work. If you're deccing a small corp that you know logs in within a certain time zone, this shouldn't me much of a problem. However, if there are many targets and you don't know in which exact time zone they live, pinging all those people becomes a major pain in the ass. This is exactly what has discouraged PV Rock from his hitman runs on miners.